Electron discharge device



p 9 2' I H.-G. LUBSZYNSKI 2,280,922

ELECTRON DISCHARGE DEVICE Filed Jan. 15, 1957 Affarney.

' multiplier. The mosaic-is Patented Apr. 28, 1942 I Bans GerhardLubszynskl, Hillingdon, England,"- assignor to Electric & MusicalIndustries Limlted, Hayes, Middlesex, England, a company of GreatBritain In Great Britain January 16, 1936 i Application January15,1937,-ScrialNo. 120,101 l 7 Claims. (cl. its-1.2)

This invention relates to electron discharge devices of the kindin whichan image of an object is projected upon a light-sensitive structure,such as a mosaic screen composed of photo-electric elements.

The invention is particularly, but not exclusively. concerned with anelectron discharge de-' vice suitable for use in the transmission ofimages,

the image of the object to be transmitted being projected on to thelight-sensitive structure for, the purpose-oi obtaining picture signalsfor trans-- mission.

It is an object of the present invention to pro-' vide an-improvedelectron discharge device which is capable of providing a larger poweroutput, such as picture signals, than has been obtainable heretofore. r

According to the present invention, an electron ranged to function inthe manner of what is known as a direct current electron multiplier orin the manner of a high frequency multiplier as hereinafter moreparticularly referred to. In order that the said invention may beclearly understood and readily carried into effect, the same will now bemore fully described with reference to the accompanying drawing inwhich- Figure 1 is a diagrammatic illustration of an electron dischargedevice in accordance with the invention and embodying an electronmultiplier of the direct current type.

discharge device for use in television and like systems comprises anevacuated envelope-containing a structure arranged to storeelectrostatic charges and permeable by electrons, a source of electronsfor producing an electron beam for scanning said structure and beingadapted to be modulated by the electrostatic charges developed in saidstructure on projection of an image thereon, a first target electrodearranged on that side of the structure remote from the source ofelectrons ands. collecting electrode or anode arranged in a positionto'receive-elec- I trons liberated as a result of impact of said cathoderay beam on'said first target electrode. The said structure ispreferably in the form of a mosaic grid-like structure oflight-sensitive elements, so constructed that when light is projectedthereon, photo-electrons are liberated causing electrostatic charges -tobe accumulated on the elements of the mosaic, according to the intensityof the incident light.

Thus, the present invention, more briefly Figure 2 is a diagrammaticillustration of a further embodiment of theinvention in which a highfrequency electron multiplier and w c Figure 3 is a modification ofFigure 2. The two examples shown are particularly for is employed use ina television transmitting system in which an image ofthe subject fortransmission is resolved into picture sion.

As shown, the electron discharge device of Figure 1 is in the form'of acathode ray tube com prising an evacuated envelope of suitable form,

not shown, containing a. mosaic 3 of photo-electrio elements, towhichmore detailedreference will be made hereinafter, and an electrongun B,

the latter comprises a cathode 5 and two anodes Band I which areadapted, when maintained at suitable positive potentials relatively tothe oathode, to act as an electron lens, and thus to focus electronsfrom the cathode upon the photo-electric elements-'0! the mosaic 3.

A preferred method of constructing the mosaic is as follows: a grid ormesh 8 is prepared of line A insulated filaments, such as glass orenamel covered wires, or the like, and a thin layer of silver is formedon one side of the grid. The coated light-sensitive structure, upon,which an optical gridis then treated, for example, by baking, to causethesilver coating to break up into discrete elements or globulesindicated generally at 9,'and

image of an object to .be transmitted is projected,

with a device of the kind known as an electronarranged to be scanned by"a cathoderay beam, and to be permeable by electrons: thescanning beamfurnishes electrons for discharging the mosaic elements, the re-,mainder of the beam passing through thev mosaic. The beam thus becomesmodulated in intensity in accordance with the potentials of the mosaic.

of the elements a photo-electric material, such as caesium, is depositedon the silver elements.

The mosaic r18 arranged within the tube with its photo-electric sidefacing the electron gun I.

- On the same side of-the mosaic is arranged a col- If desired, anelectrostatic screen may be arranged between the mosaic and the electronmultiplier. The cathode ray beam may be deflected over the mosaic by anyknown or suitable means,- such, for example, as electro-magneticdeflecting The arrangement of target and'collectins electrodes formingthe electron multiplier may be arlecting electrode II of fine wire meshfor collectother side thereof is arranged an electrostatic screen|l,"and a first target electrode arranged at an angle to the meandirection of the beam from the electron gun... so hat electrons passingthrough the mosaic impinge on the first target electrode. Means may, ifdesired, be provided for concentrating electrons on the first targetelectrode. Thescreen ll serves to shield the target electrode l2electrostatically: from the mosaic 3. Secondary electrons emitted fromthe first: target electrode may be collected directly by signalssuitable for transmis liberation of tertiary electrons.

- to the neighbourhood of the potential of the a collecting electrode,or may be caused to impinge on a second target electrode to effect theThe latter may be collected, or caused to liberate quaternary Yelectrons from a third target electrode, and so on.

In the example shown in Figure 1, secondary I electrons from the targetelectrode l2 are caused to impinge on a second target electrode l3, the

tertiary electrons liberated from the electrode I3 being collected by acollecting electrode or anode I The elements described above are ofcourse all arranged in the same evacuated envelope.

It may be arranged that the scanning beam from the electron gun 4 isdecelerated before it reaches the mosaic 3, so that the sensitivity ofthe moisaic in controlling the intensity of the electron beam isincreased. The deceleration of the beam may be effected by means 'of agrid electrode, not shown, arranged in front of the mosaic andmaintained at a suitable low potential, for example or by arranging thatthe mosaic screen is stabilised, when scanned by the beam,

cathode of the gun. I

The electron multiplier shown diagrammatically in Figure 1 may ofcourse-be associated with the usual auxiliary devices normally employedin multipliers. For example it is necessary where" more than one stageof electron multiplication to provide electrostatic or electromagneticmeans for focusing electrons liberated by one target electrode upon thenext. In the example shown electromagnetic means are employed for thispurpose, indicated bythe coils I! and 8. v

The apparatus described is employed for generating picture signals inthe following manner, the collecting electrode ID, the screen H and theelectrodes I2, I3 and M of the electron multiplier are all maintained atpositive potentials relatively to the cathode, the positive potentialsof the multiplier electrodes increasing progressivelyby suitable amountsfrom the first target multiplication occurs, thescreen.

output at picture signal frequncies'of the arrangement is relativelyhigh.

The charges held by the elements of the mosaic may be allowed, withoutdetriment, to leak away slowly to the wire cores of the constituentfilaments, since it can then readily be arranged that substantially allof the photo-electrons emitted are taken up by the collecting electrode.

The electron multiplier shown in Figure l is 'what is known as a directcurrent electron multiplier and in the embodiment of the invention shownin Figure 2 a high frequency electron multiplier is shown. In thisembodiment the cathode ray gun, mosaic screen, electrodes I0 and H arethe same as shown in Figure 1 but the cathode ray beam after modulationby the screen 3 passes through an apertured electrode 2| arrangedparallel with an electrode 22 each of which constitutes targetelectrodes of the multiplier. The electrodes 2| and 22 are maintained ata suitable relatively low positive potential and are connected to a highfrequency oscillator indicated at 23 in such a manner that theelectrodes 2| and 22, during operation, are caused to fluctuate inpotential in opposite senses. This causes the electrons rapidly tobombard the electrodes successively and at each bombardment electronsbeing eventually collected by an electrode 24 maintained at a highpositive potential. The electrodes 2|, 22 and 23 are arranged in thesame envelope as the associated elements 3, 5, 6, I, I0 and II.

Although in the specific description of the two embodiments of theinvention reference has been made to the transmission ofimages, it is tobe understood that the invention is not limited thereto as the electrondischarge device can be used for purposes or systems other thantelevision systems, for example, if desired, the collecting electrode oranode Il may be replaced by a fluorescent screen, in which case anintensified image of the object projected on the mosaic 3 will be causedto appear on the fluorescent It willbe observed from Figures I and 2that the image is projected obliquely on to the mosaic 3, whilst themean position of the cathode ray beam is normal to the said screen. Insome As the cathode ray. beam scans the screen 3,

the electrostatic charges accumulated on the ele- .ments of the-screendue to the liberation of photo-electrons which are collected by theelectrode l3, are restored to an equilibrium potential by the beam, andthus the beam becomes modulated according to the electrostatic chargeson the elements. The portion of the beam passing throughthe mosaic 3after modulation falls on the first target electrode l2. Electronmultiplication then occurs, .in two stages in the specific exampleshown, due 'to the provision of the second target electrode l3, thetertiary electrons liberated from the second target electrode l3 beingcollected by the collecting electrode or the resistance In which arethen fed to a suitable amplifier for transmission. As a result of theWith the H. F. multiplier shown in Figure 2 there is a possibility thatthe excursions of-the w electrons between the electrodes2| and 22 mayresult in some of the electrons being dissipated through the aperture inthe electrode 2|. Where, however, the image is projected on to thescreen normally and the cathode ray scans the screen 3 the modulatedelectron beam is permitted to anode I4, picture signals beingestablished across pass through the spaces between the louvres or slats25 to be accelerated'by the field between the electrodes 2| and'22.Since the louvres ,or slats are inclined, as stated above, secondaryelectrons emitted from the electrode 22 will impinge upon the louvres-orslats, such impingeprovision of the electron multiplier the power mentliberating secondary electrons which are accelerated toward theelectrode 22. Thus: there is no free passage for the secondary electronsliberated from the electrode 22 such as occurs with the constructionshown in Figure 2.

I claim: V

1. An electron discharge device suitable for use in television and likesystems, comprising an evacuated envelope containing an electronpermeable light responsive structureupon which a light im'age-is adaptedto be projected and cona mosaic, a collector electrode or anodeassociated to receive the scanning beam of electrons projected throughsaid structure, and a collecting electrode or anode arranged in aposition to receive secondary electrons liberated as a result of impactof said modulated cathode ray beam .on said, first target electrodewhereby the target electrode and the collecting electrode or anodeconstitute a direct current amplifier, at least one i electrodespositioned on the other side of said mosaic, a collector electrode oranode associated therewith, and means connected to said targettherewith, at least one of said target electrodes being adapted toreceive beam electrons which are projected through said mosaic asdetermined by the light values projected thereon, means to produce analternating high frequency field between said target electrodes toproduce electron multiplication through the production of secondaryelectrons, and means to prevent the secondary electrons so produced fromstriking the mosaic.

5. An electron discharge device comprising an evacuated envelopecontaining a light sensitive mosaic including a plurality of discreteelements upon which a light image may be projected, said mosaic beingelectron permeable, means for producing a beam of electrons adapted forscanning one side of said mosaic, a pair of opposed target electrodespositioned on the other side of said mosaic, a collector electrode oranode associated therewith, at least one of said target electfodes'being adapted to receive beam electrons which are projected through saidmpsaic as determined by the light values projected thereon, and means toproduce an alternating high frequency field between said targetelectrodes to produce elec-' tron multiplication-through the productionof secondary electrons, at least aportion of one oi said targetelectrodes being. provided with a plurality of louvres so positioned asto be parallel with the scanning beam of electrons but at-an angle tothe axis of the target electrodes, said means for producing the beam ofelectrons being positioned to scan said mosaic obliquely.

6. In electron tubeapparatus for transmitting television signals, thecombination which comprises a perforated photoelectric mosaic screenelectrodes to produce an alternating high ire,-

quency field therebetween, at least one of said target electrodes beingadaptad to receive beam electrons which are permitted to pass throughsaid mosaic in accordance with the light values projected thereon.

3. An electron discharg evacuated envelope containing 'a light-sensitivemomic including a plurality of discreteelements upon which a light imagemay beprojected, said mosaic being electron permeable, means forproducing a beam of electrons adapted for scanning one side of saidmosaic, a pair of opposed target electrodes positioned on the other sideof said mosaic, a collector electrode or anode associated therewith, atleast one of said target electrodes being adapted to receive beamelectrons which are projected-through said mosaicvin accordance with thelight values projected thereon, means.

evice comprising an ondary electron-emissive screen disposed to receivesaid electron signal current and adapted to emit secondary electronsfrom each point thereof in proportion tothe electrons received by saidpoint, said emissive screen being on the side or the mosaic screenopposite that on which the n seaming beam impinges,.a.nd means forutilizing said secondary electrons to provide a signal.

to 'produce an altemating high irequency'fleld between said targetelectrodes to produce electron multiplication through the production ofsecondary electrons, and means to restrict the movement of the secondaryelectrons to the space between the said target electrodes.

4. An electron discharge device comprising an evacuated envelopecontaining alight sensitivemosaic including a plurality of discreteelements upon which alight image may be projected, said mosaic beingelectron permeable,.means for producing a beam otelectrons adapted forscanning one side of said mosaic, a pair of opposed target correspondingsecondary electrons to its'succes-- sor, and successive screens of saidseries being disposed'to receive electrons from its predecessor andadapted to emit corresponding secondary electrons to its successor, anda final screen for I "L-In electron tube apparatus for transmittingtelevision signals, the combination which com-" 1" prises aphotoelectric mosaic screen for receiving an image of a'scene tobe-transmitted. a source of an electron scanning beam, means forscanningsaid screen with said beam to cause an electron signal currentto be emitted from imagepoints of said screen successively scanned, aseries collecting said electrons to form a s nal.

HANS LUBSZYNSKII.

